Abstract：
Plant diseases are an important threat to food production. While major pathogenicity determinants required for disease have been extensively studied, less is known on how pathogens thrive during host colonization, especially at early infection stages. Here, we used randomly barcoded-transposon insertion site sequencing (RB-TnSeq) to perform a genome-wide screen and identify key bacterial fitness determinants of the vascular pathogen Xanthomonas campestris pv campestris (Xcc) during infection of the cauliflower host plant (Brassica oleracea). This high-throughput analysis was conducted in hydathodes, the natural entry site of Xcc, in xylem sap and in synthetic media. Xcc did not face a strong bottleneck during hydathode infection. In total, 181 genes important for fitness were identified in plant-associated environments with functional enrichment in genes involved in metabolism but only few genes previously known to be involved in virulence. The biological relevance of 12 genes was independently confirmed by phenotyping single mutants. Notably, we show that XC_3388, a protein with no known function (DUF1631), plays a key role in the adaptation and virulence of Xcc possibly through c-di-GMP-mediated regulation. This study revealed yet unsuspected social behaviors adopted by Xcc individuals when confined inside hydathodes at early infection stages.
摘要：
植物病害是威胁粮食生产的重要因素。虽然疾病所需的主要致病性决定因素已被广泛研究，对病原体在宿主定植过程中如何茁壮成长知之甚少，尤其是在感染早期。这里,我们使用随机条形码转座子插入位点测序(RB-TnSeq)进行了全基因组筛选,并确定了花椰菜宿主植物(甘蓝)感染过程中血管病原体黄单胞菌(Xcc)的关键细菌适应性决定因素.这种高通量分析是在线虫中进行的，Xcc的自然入口，在木质部汁液和合成培养基中。Xcc在棘突感染期间没有面临强大的瓶颈。总的来说,在与植物相关的环境中鉴定出181个对适应性重要的基因，这些基因在代谢中具有功能富集，但以前已知仅有少数基因与毒力有关。12个基因的生物学相关性通过单突变体的表型独立证实。值得注意的是,我们显示XC_3388，一种功能未知的蛋白质(DUF1631)，可能通过c-di-GMP介导的调节在Xcc的适应和毒力中起关键作用。这项研究揭示了Xcc个体在感染早期被限制在hythrodes内时所采取的尚未被怀疑的社会行为。
